An electrochemical power source has an anode, a cathode and an electrolyte. Typical examples of electrochemical power sources are batteries and fuel cells. Batteries and fuel cells can be broadly classified according to their choice of electrolyte. Metal hydride batteries are alkaline and lead acid batteries are acidic. Common examples of fuel cells are phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC), alkaline fuel cells (AFC), proton exchange membrane fuel cells (PEMFC), and solid oxide fuel cells (SOFC). Each of these uses only a single electrolyte. For example, phosphoric acid fuel cells use a saturated phosphoric acid electrolyte supported in an inert porous matrix, and alkaline fuel cells use an alkaline medium as an electrolyte.
An important characteristic used for comparing the performance of different cells is the open circuit voltage (OCV), which is the voltage across the cell when no current is drawn. In addition to being related to the voltage-current characteristics of a cell, the OCV can be calculated from thermodynamics. In batteries using aqueous electrolytes such as the lead-acid battery, the OCV is less than 2.0V (D. Linden and T. B. Reddy, “Handbook of Batteries”, McGraw-Hill, 2002). A hydrogen-oxygen fuel cell has a theoretical OCV of 1.229 V, regardless of whether the electrolyte is alkaline or acidic. In reality, most non-metal fuels in fuel cells of various electrolytes have an OCV of about 1 volt (J. Larminie and A. Dicks, “Fuel Cell Systems Explained, ” John Wiley Press, 2000).
In general, an increased operating voltage for a single cell will result in additional power and energy, and thus will be very advantageous for the practical application of batteries and fuel cells. Higher voltages are only possible by arranging multiple cells into a stack system. By a novel choice and design of electrolytes and membrane, the present invention provides a >30% increase in voltage and power in some batteries and a 50% increase in voltage and power in fuel cells. Since fuel cells are classified by their electrolytes, this novel use of more than one electrolyte will lead to a new class of fuel cells.